MONTOUR, Iowa — After candidate entries and candidate withdrawals, debates and debate-related controversies, campaign surges and campaign duds, and tens of millions spent and tens of millions wasted on broadcast advertisements, we finally have reached the actual election year.

No one expected Donald J. Trump to retain his high poll ratings. No one expected Gov. Scott Walker of Wisconsin to bomb. No one expected terrorism to emerge as a top issue. No one expected Republican politics to be so riveting.

But though some of the candidates have been on a fool’s errand, the year 2015 was not a bootless errand. It has taught us a lot about the nature of our politics, and there’s a good argument to be made that the year 2015 was more valuable than any year preceding an election since 1975, when the country began to heal its Watergate wounds.

Here are some of the lessons we learned:

• This election is about a profound transfer of power and control. Everywhere the establishment is in eclipse. Here in Iowa, despite a history of rural rebellion, for generations the Farm Bureau and the leaders of the soybean association, the corn growers, the hog producers association and the cattlemen’s organizations set the boundaries for acceptable thought and rhetoric and subtly guided the debate. No more.

“Today, most of the county leadership in Iowa is from the fundamentalist churches with a few libertarians,” says James Leach of the University of Iowa, a three-decade veteran of Congress from this state. “The country club has been pushed aside. In some ways this is quite impressive.”

This phenomenon in the Republican Party has a bizarre analogue in the Democratic Party, where the establishment has an unusual tint. It is headed not by the minority leaders of Des Moines nor by the labor leaders of Iowa’s farm-implement factories but instead by supporters of a former secretary of state who was a student leader at Wellesley College during the protest era of the 1960s and her husband, a former president who maneuvered to avoid the draft, was involved in the protest politics of the late 1960s and early 1970s, and was impeached for imprudent sexual behavior.

• The tension between insiders and outsiders has been resolved. The insiders have lost. That’s why the names John Boehner, recently departed speaker of the House, and Mitt Romney, the most recent Republican presidential nominee, are never uttered here — not on the campaign trail, not in casual political conversations, not even in analysts’ comments about the state of the new GOP.

“There’s a huge rebellion against people like them,” says Hans Hassell, a political scientist at Cornell College in Mount Vernon, Iowa. That rebellion is being waged against the traditions of earlier Republican victors in Iowa caucuses past, such as former Senate Majority Leader Robert J. Dole of Kansas, a consummate legislative dealmaker and the winner of the 1988 caucuses.

Mr. Hassel believes there has been a significant change in the temper of politics in Iowa, which, except in periods of rural economic crisis, customarily has been exceedingly civil, even accommodating. “We have the emergence of no-compromise candidates in a system that functions with compromise,” he says. “It’s a question of approach to government, and that’s where the pressure points are.”

• A country that once was optimistic now is angry. You do not have to attend a Trump rally to feel the electorate seethe, and the candidates who have channeled that anger (and who have spawned even more anger) are the ones who are prospering as this new year opens.

This anger is in response to massive changes sweeping the country and the world, from immigration (everywhere) to the economy (still in transition) to national security (a problem throughout the world, especially in the Middle East and Russia) to personal security (the unease Americans feel in movie theaters, stadiums, hotels and schools).

“This campaign is about finding our way in a period of volatility and unrest,” says Barbara Trish, a political scientist at Iowa’s Grinnell College. “There are overseas challenges, a recovery that’s not yet finished, and battles that don’t seem to go away.”

• An angry country is open to a presidential campaign by angry candidates. In ordinary circumstances, candidates with steady demeanors and solid executive experience such as former Gov. Jeb Bush of Florida and Gov. John Kasich of Ohio — even former Gov. George Pataki of New York, who just departed the race — would be soaring in the polls. They’re not. They’re struggling.

Indeed, they seem completely out of synch with the times: They’re black-and-white actors in a Technicolor age. They’re singing Sinatra when the country is listening to Miley Cyrus. They’re lining up in a single-wing formation with a tailback, fullback and wingback while the rest of football employs a single running back.

Mr. Trump is the quintessential candidate of this anger, and so is Sen. Ted Cruz of Texas. Gov. Chris Christie of New Jersey was born for this role. Sen. Marco Rubio of Florida has similar positions but a more mellow mien. He’s sipping Diet Sierra Mist while the other three are downing bone-dry martinis.

• The pundits and scholars may look askance at the important roles played by Iowa, which on Feb. 1 holds the first caucuses, and New Hampshire, which on Feb. 9 holds the first primary, but their value may be greater than ever.

Here in Iowa the candidates have been forced to meet, sometimes in tiny groups, with real voters who are not scripted and not reluctant to share their views. These voters may have inflamed some of the candidates, but they also gave these candidates ground-level assessments of how life is lived in America in the second decade of the 21st century.

Two decades ago, a prominent Iowan, John Chrystal, a onetime candidate for governor and Iowa’s longtime agricultural link to the Soviet Union, which bought seed corn from here, wrote a tribute to his home state. “No place holds a candle to Iowa,” wrote Mr. Chrystal, who died in 2000. “Its natural production jumps at you, and its lushness is overpowering. The air is pure, the people wonderful and integrity and honesty a way of life.”

He might have added that political acuity is also a way of life — especially in the winter of American presidential elections.

David Shribman, a Pulitzer Prize winner in journalism, is executive editor of the Pittsburgh Post-Gazette.